Semiconductor device

ABSTRACT

A semiconductor device includes a first pMISFET region having an Si channel, a second pMISFET region having an Si channel and an nMISFET region having an Si channel. First SiGe layers which apply first compression strain to the Si channel are embedded and formed in the first pMISFET region to sandwich the Si channel thereof and second SiGe layers which apply second compression strain different from the first compression strain to the Si channel are embedded and formed in the second pMISFET region to sandwich the Si channel thereof.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromprior Japanese Patent Application No. 2007-088836, filed Mar. 29, 2007,the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a semiconductor device and a manufacturingmethod thereof, and more particularly, to a semiconductor device inwhich the mobility is enhanced by embedding silicon germanium (SiGe) insource/drain regions of MISFETs and straining Si channels and amanufacturing method of the semiconductor device.

2. Description of the Related Art

As a manufacturing method of CMOS transistors having high drivability,the technique (so-called strained Si technique) for enhancing themobility by straining silicon (Si) and applying stress to channelregions is known. Particularly, as one example of an element structuremanufactured by the use of the strained Si technique, an eSiGe techniquegains much attention. The eSiGe technique is a method for enhancing themobility by embedding SiGe layers in the source/drain regions of pMISFETregions and applying compression stress to the Si channel regions (forexample, refer to U.S. Pat. No. 6,621,131).

In the structure in which the SiGe layers are embedded in thesource/drain regions of the pMISFET, stress to the channel regionincreases in proportion to the germanium (Ge) concentration in the SiGelayers. Therefore, the mobility is more enhanced as the Ge concentrationbecomes higher. However, since a risk caused by crystal defects in theSiGe layer becomes higher in proportion to the Ge concentration, thereis a possibility that a problem of abnormal growth of salicide orjunction leak (J/L) will occur when the Ge concentration becomes high.

In an LSI, not only elements having high drivability but also elementshaving high reliability are required. When the Ge concentration in theSiGe layer is made higher in order to manufacture elements having thehigh drivability, a risk due to the crystal defects in the SiGe layerincreases, and as a result, the high reliability cannot be attained.That is, in the conventional method, both of pMISFETs having the highdrivability and pMISFETs having the high reliability cannot be formedtogether in one chip.

BRIEF SUMMARY OF THE INVENTION

According to one aspect of the present invention, there is provided asemiconductor device which includes a semiconductor substrate, a firstpMISFET region formed on the semiconductor substrate and having a firstSi channel, first SiGe layers which apply first compression strain tothe first Si channel being embedded and formed in the first pMISFETregion to sandwich the first Si channel, a second pMISFET region formedon the semiconductor substrate to be electrically isolated from thefirst pMISFET region and having a second Si channel, second SiGe layerswhich apply second compression strain different from the firstcompression strain to the second Si channel being embedded and formed inthe second pMISFET region to sandwich the second Si channel, and annMISFET region formed on the semiconductor substrate to be electricallyisolated from the first and second pMISFET regions and having a third Sichannel.

According to another aspect of the present invention, there is provideda manufacturing method of a semiconductor device which includes forminga first pMISFET region, second pMISFET region and nMISFET region whichare electrically isolated from one another by forming an elementisolation region on a well on an Si substrate, forming a first maskwhich covers the second pMISFET region and nMISFET region, selectivelyembedding and forming first SiGe layers which apply first compressionstrain to an Si channel of the first pMISFET region in the first pMISFETregion by the use of the first mask, removing the first mask afterformation of the first SiGe layers, forming a second mask which coversthe first pMISFET region and nMISFET region after removing the firstmask, and selectively embedding and forming second SiGe layers whichapply second compression strain different from the first compressionstrain to an Si channel of the second pMISFET region in the secondpMISFET region by the use of the second mask.

According to still another aspect of the present invention, there isprovided a manufacturing method of a semiconductor device which includesforming a first pMISFET region, second pMISFET region and nMISFET regionwhich are electrically isolated from one another by forming an elementisolation region on a well on an Si substrate, forming a mask whichcovers the nMISFET region, forming recesses to sandwich Si channels ofthe first and second pMISFET regions by selectively etching the firstand second pMISFET regions under a condition that Si aperture ratios ofthe first and second pMISFET regions are made different with the nMISFETregion covered with the mask in a case where a ratio of an area of anexposed Si substrate to an entire area of one cell region containing oneMISFET region and an element isolation region surrounding the MISFETregion is defined as an Si aperture ratio, and forming first SiGe layerswhich apply first compression strain to the Si channel of the firstpMISFET region in the recesses of the first pMISFET region and formingsecond SiGe layers which apply second compression strain different fromthe first compression strain to the Si channel of the second pMISFETregion in the recesses of the second pMISFET region.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a cross-sectional view showing the schematic structure of asemiconductor device according to a first embodiment of this invention.

FIGS. 2A to 2L are cross-sectional views showing manufacturing steps ofthe semiconductor device according to the first embodiment.

FIG. 3 is a cross-sectional view showing the schematic structure of asemiconductor device according to a modification of the firstembodiment.

FIG. 4 is a cross-sectional view showing the schematic structure of asemiconductor device according to a second embodiment of this invention.

FIGS. 5A and 5B are plan views showing the relationship between the Siaperture ratios of first and second pMISFET regions.

FIG. 6 is a characteristic diagram showing the relationship between theSi aperture ratio in the growing process of an SiGe layer and the Geconcentration.

FIGS. 7A and 7B are plan views showing examples in which the Si apertureratios of the first and second pMISFET regions are changed by changingthe gate lengths.

FIGS. 8A and 8B are plan views showing examples in which the Si apertureratios of the first and second pMISFET regions are changed by changingthe width W and length X of a MISFET region.

FIGS. 9A and 9B are plan views showing examples in which the Si apertureratios of the first and second pMISFET regions are changed by using aregion which is not associated with a circuit.

FIGS. 10A to 10D are cross-sectional views showing manufacturing stepsof the semiconductor device according to the second embodiment.

DETAILED DESCRIPTION OF THE INVENTION

There will now be described embodiments of the present invention withreference to the accompanying drawings. The following contents are shownas embodiments of this invention and this invention is not limited tothe following contents.

First Embodiment

FIG. 1 is a cross-sectional view showing the schematic structure of asemiconductor device according to a first embodiment of this invention.

An element isolation insulating film 110 is formed on a surface portion(well) of an Si substrate 100 and a first pMISFET region 121, secondpMISFET region 122 and nMISFET region 123 are formed in portionssurrounded by the element isolation insulating film 110. A gateelectrode 301 is formed above the pMISFET region 121 with a gateinsulating film 130 disposed therebetween and source/drain regions areformed with the gate electrode 301 used as a mask so as to form a firstp-channel MIS transistor. A gate electrode 302 is formed above thepMISFET region 122 with a gate insulating film 130 disposed therebetweenand source/drain regions are formed with the gate electrode 302 used asa mask so as to form a second p-channel MIS transistor. Further, a gateelectrode 303 is formed above the nMISFET region 123 with a gateinsulating film 130 disposed therebetween and source/drain regions areformed with the gate electrode 303 used as a mask so as to form an nMIStransistor.

In the first pMISFET region 121, first SiGeB films 321 are formed in thesource/drain regions which sandwich the Si channel. The SiGeB film 321is formed by doping B used as a p-type impurity into the SiGe layerwhich applies compression strain to the Si channel, and as a result, themobility in the first pMIS transistor is enhanced. Likewise, in thesecond pMISFET region 122, second SiGeB films 322 are formed in thesource/drain regions which sandwich the Si channel. Like the SiGeB film321, the SiGeB film 322 also applies compression strain to the Sichannel, and as a result, the mobility in the second pMIS transistor isenhanced.

The first SiGeB films 321 formed in the first pMISFET region 121 and thesecond SiGeB films 322 formed in the second pMISFET region 122 aredifferent in the Ge concentration. That is, the Ge concentration of thefirst SiGeB film 321 is higher than that of the second SiGeB film 322.Therefore, stresses applied to the respective Si channels of the firstand second pMISFET regions 121 and 122 are different.

More specifically, the compression stress applied to the Si channel ofthe first pMISFET region 121 is larger than the compression stressapplied to the Si channel of the second pMISFET region 122. Therefore,the strain amount for the Si channel of the first pMISFET region 121becomes larger than the strain amount for the Si channel of the secondpMISFET region 122. As a result, the first pMISFET region 121 issuitable for formation of elements having high drivability and thesecond pMISFET region 122 is suitable for formation of elements havinghigh reliability.

Next, the manufacturing method of the semiconductor device according tothe present embodiment is explained with reference to FIGS. 2A to 2L.

First, as shown in FIG. 2A, an Si substrate 100 having an elementisolation insulating film 110 formed on a well of the surface portion isprepared. On the Si substrate 100, a first pMISFET region 121, secondpMISFET region 122 and pMISFET region 123 which are isolated from oneanother by the element isolation insulating film 110 are formed.

Then, a gate insulating film 130 is formed on the entire surface of theSi substrate 100 by the use of a low-pressure chemical vapor deposition(LPCVD) method. For example, a material of the gate insulating film 130is a silicon oxide film (SiO2), silicon oxynitride film (SiON) orferroelectric gate insulating film (Hi-k) and the thickness thereof is 2nm. After this, a polysilicon film 140 is formed on the entire surfaceof the gate insulating film 130 by the use of the LPCVD method. Thethickness of the polysilicon film 140 is 100 nm.

Next, a resist pattern 210 is formed on the polysilicon film 140 tocover the nMISFET region 123 by the use of lithography. Then, boron (B)is implanted into a portion of the polysilicon film 140 which lies abovethe first and second pMISFET regions 121 and 122 by the use of anion-implantation technique with the resist pattern 210 used as a mask.

As shown in FIG. 2B, a p⁺-type polysilicon film 141 is formed above thefirst and second pMISFET regions 121 and 122 by the aboveion-implantation process of B. After this, the resist pattern 210 isremoved by wet etching.

Next, as shown in FIG. 2C, a resist pattern 220 is formed to cover thefirst and second pMISFET regions 121 and 122 by the use of lithography.Then, phosphorus (P) is implanted into the polysilicon film 140 with theresist pattern 220 used as a mask.

As shown in FIG. 2D, an n⁺-type polysilicon film 142 is formed above thenMISFET region 123 by the above ion-implantation process of P. Afterthis, the resist pattern 220 is removed by wet etching.

Next, as shown in FIG. 2E, a hard mask 160 is formed on the entiresurface of the resultant structure by the use of the LPCVD method. Forexample, the hard mask 160 is a composite film containing TEOS andsilicon nitride (SiN), the thickness of TEOS is 40 nm and the thicknessof SiN is 60 nm. Then, a first gate electrode pattern 231, second gateelectrode pattern 232 and third gate electrode pattern 233 formed ofresist are formed on the hard mask 160 by the use of lithography.

Next, as shown in FIG. 2F, a first gate electrode 301, second gateelectrode 302 and third gate electrode 303 are formed by the use of areactive ion etching (RIE) method. Specifically, the hard mask 160 isselectively etched by the use of the RIE method while the electrodepatterns 231, 232 and 233 formed of resist are used as a mask. Then, thep⁺-type polysilicon film 141 and n⁺-type polysilicon film 142 areselectively etched by the use of the RIE method while the thus etchedhard masks 160 are used as a mask so as to form the gate electrodes 301,302, 303. After this, the first gate electrode pattern 231, second gateelectrode pattern 232 and third gate electrode pattern 233 are removedby wet etching.

Next, as shown in FIG. 2G, a tin film 170 used as sidewall films isformed by the use of the LPCVD method. A material of the thin film 170is TEOS, for example, and the thickness thereof is 40 nm. As the thinfilm 170, SiN can be used instead of TEOS. Then, a resist pattern 240 isformed to cover the second pMISFET region 122 and nMISFET region 123 bythe use of lithography.

Next, as shown in FIG. 2H, in the first pMISFET region 121, the thinfilm 170 is left behind only on the sidewalls of the gate electrode 301by selectively etching the thin film 170 by a preset amount by the useof the RIE method. That is, sidewall films 171 are formed on the gateside portions of the first pMISFET region 121. Then, recesses 181 whichsandwich the Si channel are formed in the first pMISFET region 121 bywet etching. For example, the depth of the recess 181 is 60 nm.

Next, as shown in FIG. 2I, first SiGeB films 321 are grown and formed inthe recesses 181 by the use of the LPCVD method. The thickness of thefirst SiGeB film 321 is 60 nm and the Ge concentration thereof is 20%. Bin the SiGeB film 321 acts as a p-type impurity and it is possible todope an impurity other than B.

Next, as shown in FIG. 2J, after the thin film 170 and sidewall films171 are removed by wet etching, a thin film 190 used sidewall films isformed by the use of the LPCVD method. A material of the thin film 190is TEOS, for example, and the thickness thereof is 40 nm. Then, a resistpattern 250 is formed to cover the first pMISFET region 121 and nMISFETregion 123 by the use of lithography.

Next, as shown in FIG. 2K, in the second pMISFET region 122, the thinfilm 190 is left behind only on the sidewalls of the gate electrode 302by selectively etching the thin film 190 by a preset amount by the useof the RIE method. That is, sidewall films 191 are formed on the gateside portions of the second pMISFET region 122. Then, recesses 182 whichsandwich the Si channel are formed in the second pMISFET region 122 bywet etching. For example, the depth of the recess 182 is 60 nm. In thiscase, the depths of the recesses 181 and 182 may be made different.

Next, as shown in FIG. 2L, second SiGeB films 322 are grown and formedin the recesses 182 by the use of the LPCVD method. The thickness of thesecond SiGeB film 322 is 60 nm and the Ge concentration thereof is 15%.That is, the Ge concentration of the second SiGeB film 322 is lower thanthat of the first SiGeB film 321.

After this, the thin film 190 and sidewall films 191 are removed by wetetching and the semiconductor device with the structure shown in FIG. 1can be attained.

Although not shown in FIG. 1, extension layers may be formed between thefirst SiGeB films 321 and the channel region below the gate electrode301 in the first pMISFET region 121 and extension layers may be formedbetween the second SiGeB films 322 and the channel region below the gateelectrode 302 in the second pMISFET region 122.

Thus, in the present embodiment, the strain amount for the first pMISFETregion 121 is set larger than the strain amount for the second pMISFETregion 122 by making different the GE concentrations of the first SiGeBfilm 321 formed in the first pMISFET region 121 and the second SiGeBfilm 322 formed in the second pMISFET region 122. Ideally, the GEconcentration of the SiGeB film 321 in the first pMISFET region 121required to have the high drivability is set in a range of 18 to 30% andthe GE concentration of the SiGeB film 322 in the second pMISFET region122 required to have the high reliability is set in a range of 5 to 15%.

Therefore, the transistor in the first pMISFET region 121 has highdrivability and the transistor in the second pMISFET region 122 has highreliability. That is, a pMISFET having high drivability and a pMISFEThaving high reliability can be formed together in one chip. Therefore,the quality of a CMOS transistor can be enhanced.

The strain amount of the Si channel depends on the GE concentration ofthe SiGeB films which sandwich the Si channel but it also depends on thethickness of the SiGeB film. The strain amount becomes larger as theSiGeB film becomes thicker. Therefore, as shown in FIG. 3, the Sichannel strain for the first pMISFET region 121 can be made larger bymaking different the depths of the recesses 181 and 182 in the firstpMISFET region 121 and second pMISFET region 122 and forming the firstSiGeB film 321 thicker than the second SiGeB film 322. Ideally, thedepth of the SiGeB film 321 in the pMISFET region 121 required to havethe high drivability is set in a range of 75 to 100 nm and the depth ofthe SiGeB film 322 in the pMISFET region 122 required to have the highreliability is set in a range of 30 to 60 nm.

With the above structure, the strain amount for the first pMISFET region121 can be set larger than the strain amount for the second pMISFETregion 122 and the quality of a CMOS transistor can be enhanced.Further, not only one of the Ge concentration and the recess depth ischanged but also both of them can be changed.

Second Embodiment

FIG. 4 is a cross-sectional view showing the schematic structure of asemiconductor device according to a second embodiment of this invention.The same symbols are attached to the same portions as those of FIG. 1and the detail explanation thereof is omitted.

The present embodiment is different from the first embodiment in thatthe areas of element isolation insulating films in the respectivepMISFET regions are made different in order to change the Geconcentrations in the SiGe films. That is, as shown in FIGS. 5A and 5B,the areas of element isolation insulating films 110 in a first pMISFETregion 121 and second pMISFET region 122 are made different. The area ofthe element isolation insulating film 110 is made larger in the firstpMISFET region 121, and as a result, the area of the first pMISFETregion 121 is made smaller than that of the second pMISFET region 122.

In this case, in one cell region containing a MISFET region and elementisolation region, the ratio of an exposed area of an Si substrate to theentire area of the cell region is defined as an Si aperture ratio. Morespecifically, the ratio of the area in which the SiGe film is formed inan area of 1 mm² near the MISFET region is defined as an Si apertureratio. By changing the Si aperture ratio, the Ge concentration in theSiGe film can be changed. Examples of FIGS. 5A and 5B are obtained bychanging the areas of the element isolation insulating films 110 tochange the Si aperture ratios.

Specifically, the Si aperture ratio in the range of 1 mm² of the pMISFETregion 121 required to have the high drivability is set lower than theSi aperture ratio in the range of 1 mm² of the pMISFET region 122required to have the high reliability by at least 5%. For example, theSi aperture ratio of the pMISFET region 121 is set to 5% and the Siaperture ratio of the pMISFET region 122 is set to 10%.

FIG. 6 is a characteristic diagram showing the relationship between theSi aperture ratio and the Ge concentration of an SiGe layer grown. It isunderstood that the Ge concentration becomes higher as the Si apertureratio becomes lower. Further, the same result was obtained in a casewhere B was doped as an impurity.

In the case of FIG. 4, the first and second pMISFET regions 121 and 122are arranged close to each other, but in an actual device, since theregions are sufficiently separated, the relationship as shown in FIG. 6is established.

Thus, by setting the Si aperture ratio of the first pMISFET region 121lower than that of the second pMISFET region 122, the Ge concentrationof the SiGe layer 321 formed in the first pMISFET region 121 can beenhanced and the strain amount of the Si channel in the first pMISFETregion 121 can be made larger. In this case, it is not necessary toseparately grow SiGe layers in the first and second pMISFET regions 121and 122 and it is possible to simultaneously form the SiGe layers.Therefore, the process can be simplified.

As a method for changing the Si aperture ratio, not only the method forchanging the areas of the pMISFETs but also the following method can beconsidered.

FIGS. 7A and 7B show examples in which the Si aperture ratios arechanged by changing the dimensions of gate electrodes. FIG. 7A shows thefirst pMISFET region 121 and FIG. 7B shows the second pMISFET region122. By making the gate length of the gate electrode 301 in the firstpMISFET region 121 larger than that in the second pMISFET region 122,the Si aperture ratio of the first pMISFET region 121 can be set lowerthan that of the second pMISFET region 122.

FIGS. 8A and 8B show examples in which the length X in the gatelengthwise direction of pMISFET formation regions and the length W inthe gate width direction are changed. FIG. 8A shows the first pMISFETregion 121 and FIG. 8B shows the second pMISFET region 122. By settingW×X in the first pMISFET region 121 smaller than that in the secondpMISFET region 122, the Si aperture ratio of the first pMISFET region121 can be set lower than that of the second pMISFET region 122.

FIGS. 9A and 9B show a method for changing the Si aperture ratio withoutchanging the areas and gate lengths of the pMISFET formation regions.FIG. 9A shows the first pMISFET region 121 and FIG. 9B shows the secondpMISFET region 122. Generally, regions 510 (insulating films of SiO₂which are the same as the element isolation insulating film) which donot contribute to the operation of the circuit are formed in theperipheral portions of the MISFET regions. The region 510 is left behindas it is in the first pMISFET region 121 and part of the region 510which does not contribute to the operation of the circuit is etched inthe second pMISFET region 122 to expose the underlying Si substrate. Asa result, the Si aperture ratio of one cell region containing the firstpMISFET region 121 can be made lower than that of one cell regioncontaining the second pMISFET region 122.

The Si aperture ratio is explained with respect to the MISFET formationregion or one cell region, but in an actual device, a plurality ofelements required to have a high-speed operation and a plurality ofelements required to have high reliability are formed in separateregions in many cases. Therefore, the ratio of an exposed area of Si tothe area of an entire region in which the element group is arranged isdefined as an Si aperture ratio and the Si aperture ratios for theentire region in which the element group required to have the high-speedoperation is arranged and for the entire region in which the elementgroup required to have the high reliability is arranged may be madedifferent.

Next, a manufacturing method of the semiconductor device of the presentembodiment is explained with reference to FIG. 10. In this example, amethod for changing the areas of the pMISFET regions to change the Siaperture ratios in the two pMISFET regions 121, 122 as shown in FIGS.5A, 5B is provided.

First, like the first embodiment, an element isolation insulating film110 is formed on an Si substrate 100 and gate electrodes 301, 302, 303are respectively formed above a first pMISFET region 121, second pMISFETregion 122 and nMISFET region 123 with respective gate insulating films130 disposed therebetween. The process up to the above step is the sameas the process of FIGS. 2A to 2F. However, the element isolationinsulating film 110 is different in size in the pMISFET regions 121,122. That is, as shown in FIGS. 5A, 5B, the area of the first pMISFETregion 121 is made smaller than that of the second pMISFET region 122.Thus, the Si aperture ration in the first pMISFET region 121 is madelower than that in the second pMISFET region 122.

In the present embodiment, as shown in FIG. 10A, after a thin film 170used as sidewall films is formed by the use of the LPCVD method afterthe step of FIG. 2F, a resist pattern 260 which covers the nMISFETregion 123 is formed by the use of lithography.

Then, as shown in FIG. 10B, the thin film 170 is left behind only on thesidewalls of the gate electrodes 301, 302 by selectively etching thethin film 170 by a preset amount by the use of the RIE method. That is,first sidewall films 171 are formed on the gate side portions of thefirst pMISFET region 121 and second sidewall films 172 are formed on thegate side portions of the second pMISFET region 122.

After this, as shown in FIG. 10C, recesses 581 are formed in the firstpMISFET region 121 by wet etching, and at the same time, recesses 582are formed in the second pMISFET region 122. In this case, the depths ofthe recesses 581, 582 are both set to 60 nm. The depths of the recesses581, 582 may be made different.

Next, as shown in FIG. 10D, first SiGeB films 321 are grown and formedin the recesses 581 and second SiGeB films 322 are grown and formed inthe recesses 582 by the use of the LPCVD method. At this time, since theSi aperture ratio of the first pMISFET region 121 is lower than that ofthe second pMISFET region 122, the Ge concentration and B concentrationof the first SiGeB films 321 become higher than those of the secondSiGeB films 322.

Next, the first sidewall films 171, second sidewall films 172 and thinfilm 170 are removed by wet etching to attain the structure shown inFIG. 4.

According to the present embodiment, the Ge concentration of the firstSiGeB films 321 in the first pMISFET region 121 can be made higher thanthat in the second pMISFET region 122 by utilizing the difference in theSi aperture ratios of the two pMISFET regions 121, 122. Therefore, thestrain amount for the first pMISFET region 121 in the same chip can bemade larger than the strain amount for the second pMISFET region 122 andthe same effect as that of the first embodiment can be attained.Further, since it is not necessary to separately form masks for thefirst pMISFET region 121 and second pMISFET region 122, the number ofsteps of a mask process can be reduced and an advantage that the processis simplified can be attained.

(Modification)

This invention is not limited to the above embodiments. In the aboveembodiments, the SiGeB film is used as one example of the SiGe layer,but an SiGeC film may be used instead of the SiGeB film. That is, notonly the SiGe layer but also a layer obtained by doping impurity intoSiGe can be used.

Further, in the above embodiment, the strain amounts applied to the Sichannels in the first and second pMISFET regions are changed by changingthe Ge concentration in the SiGe layer, but the strain amount can alsobe changed by changing the thickness of the SiGe layer. Specifically,the strain amount can be made larger as the thickness of the SiGe layerbecomes larger. Therefore, transistors with the high drivability can beformed in the first pMISFET region and transistors with the highreliability can be formed in the second pMISFET region by making the Sietching depth larger in the first pMISFET region and making the Sietching depth smaller in the second pMISFET region.

In the above embodiments, the explanation is made with reference to thepMISFET regions, but in this invention, the same effect can be attainedby changing the C concentration when C-doped Si regions are formed tosandwich the Si channel in the nMISFET region.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

1. A semiconductor device comprising: a semiconductor substrate, a firstpMISFET formed on the semiconductor substrate and having a first Sichannel formed on a surface of the semiconductor substrate, and firstSiGe layers, which apply first compression strain to the first Sichannel, embedded in the surface of the semiconductor substrate tosandwich the first Si channel, a second pMISFET formed on thesemiconductor substrate to be electrically isolated from the firstpMISFET and having a second Si channel formed on a surface of thesemiconductor substrate, and second SiGe layers, which apply secondcompression strain different from the first compression strain to thesecond Si channel, embedded in the surface of the semiconductorsubstrate to sandwich the second Si channel, and an nMISFET formed onthe semiconductor substrate to be electrically isolated from the firstpMISFET and the second pMISFET and having a third Si channel formed on asurface of the semiconductor substrate.
 2. The semiconductor deviceaccording to claim 1, wherein the first and second SiGe layersrespectively contain B or C as an impurity.
 3. The semiconductor deviceaccording to claim 1, wherein Ge concentrations of the first and secondSiGe layers are different.
 4. The semiconductor device according toclaim 1, wherein depths of the first and second SiGe layers from thesurface of the substrate are different.
 5. The semiconductor deviceaccording to claim 1, wherein Si aperture ratios of the first pMISFETand the second pMISFET are different in a case where a ratio of an areaof an exposed Si substrate to an area of 1 mm² including one cell regioncontaining one MISFET therein and an element isolation regionsurrounding the MISFET is defined as an Si aperture ratio.